The Tissue Core (CORE C) mandate is to provide a national resource that consists of a dataset of matched samples of frozen cells with corresponding pathological and clinical data. The Tissue Core is an integral and essential component of this proposal since it is the central repository for all samples. It maintains accurate records of the trafficking of all samples and facilitates the uniform sharing of information between all CRC projects. In addition, it facilitates and expedites the research of each CRC project and clinical trials by performing centralized standardized assays and distributing characterized samples to all members of this proposal. This Core ensures the long-term physical integrity of the biospecimen and maintains the privacy and confidentiality of the research participant. The first aim of this Core is to serve as the central biorepository for all CLL samples diagnosed and collected from the participating clinical sites. This enables the uniform processing, storage, and distribution of all CLL samples used by the investigators of this proposal. The second aim is to perform a basic set of standardized assays on all viably stored CLL samples from each patient upon initial receipt, and as required by the clinical protocols. The third aim is to acquire serial samples during the disease progression of all CLL patients to enable longitudinal studies on the disease progression. CRC investigators can segregate cases that have indolent and non-progressive disease from those who have progressive disease or from those who have a change in the kinetics of disease progression. The fourth aim, a multi-site service, is to organize and assure accurate scoring and high quality data entry associated with FISH for CLL among all CRC sites. This service provides reliable cytogenetic data for clinical trials and research correlations. The fifth aim is to characterize CLL samples based on their cellular kinetics. As an adjunct to these studies, the expressed immunoglobulin heavy chain genes (IGHV) about the leukemic clones can then be correlated to cellular kinetics to study the role for (auto) antigen drive in the clonal expansion. Lastly, the sixth aim is to manage the distribution and tracking of specific characterized samples as requested for hypothesis-driven studies of this proposal.